1. Field of the Invention
The present invention relates to a motorcycle comprising a vehicle speed sensor such that the teeth of a gear constituting a torque transmission mechanism for transmitting a drive torque from a power unit to a drive wheel constitute a portion to be detected.
2. Description Background Art
In the motorcycle disclosed in Japanese Patent No. 3209663, a sensor constituting a rear wheel rotational speed device is mounted to a gear case connected to the rear end of a rear fork, and the tip end of the sensor is formed slantly along the tooth surface of a first rear gear of a rear-side bevel gear. This ensures that it is unnecessary to provide a multiple-toothed rotor separately from the first rear gear, as a portion to be detected by the sensor for detecting the rotational speed of the rear wheel.
In the sensor disclosed in Japanese Patent No. 3209663, the tip end thereof is slanted to be along the tooth surface of the first rear gear, while an inserted portion inserted in a gear case extends along a direction orthogonal to the rotational centerline of the first rear gear, so that the tip end extends in a direction different from the direction in which the tip end is opposed to the tooth surface. Therefore, a versatile sensor such that the direction in which the tip end is opposed to the tooth surface and the direction in which the inserted portion extends coincide with each other cannot be used. Thus, this sensor leads to a high cost. Further, since the inserted portion extends in a direction orthogonal to the rotational centerline of the first rear gear, the projection amount of the sensor on the outside in the radial direction of the first rear gear is large. Therefore, it is impossible to compactly dispose the sensor on the outside in the radial direction of the first rear gear. In relation to members disposed in the vicinity of the sensor, there arise limitations in the layout of the sensor and in the laying of electric wires connected to the sensor. In addition, where the sensor is covered with a cover, the cover would be large. Thus, the gap between the tip end of the sensor and the tooth surface which has a relationship with the detection accuracy varies depending on the mount position in the circumferential direction of the sensor, for example, the mount position in the circumferential direction with the center axis line as a center, so that an adjustment of the gap between the tip end of the sensor and the tooth surface takes time, and the mountability of the sensor is poor.